From: georgeoliverGO@...
Date: 2006-10-16T02:45:14+09:00
Subject: another basic question about sorting w/o the sort method

Hi,

I worked through the exercise in Chris Pine's tutorial where you sort
an array without using the sort method
(http://pine.fm/LearnToProgram/?Chapter=07), and I got a working
solution, but I'm curious about how to improve it. Can anyone offer
some tips? I've looked at a couple of solutions here like this one:

   def bubblesort(a)
        (a.length-1).downto(0) do |i|
            puts a.to_s
            0.upto(i-1) do |j|
                if a[j] > a[j+1]
                    a[j], a[j+1] = a[j+1], a[j] # swap
                end
            end
        end
    end

(from
http://groups.google.com/group/comp.lang.ruby/tree/browse_frm/thread/410b0ac3d37b2c5e/67afd36eba0bd5ec?rnum=1&q=sort+pine+exercise&_done=%2Fgroup%2Fcomp.lang.ruby%2Fbrowse_frm%2Fthread%2F410b0ac3d37b2c5e%2F35a2dc683df509a7%3Flnk%3Dgst%26q%3Dsort+pine+exercise%26rnum%3D2%26#doc_35a2dc683df509a7)

This is pretty much over my head but it looks a lot cooler. I would
like to write this way. What I don't understand about the above is
this:

                if a[j] > a[j+1]
                    a[j], a[j+1] = a[j+1], a[j] # swap

I'm reading this to mean if the jth position in a is lexically greater
than the jth + 1 position, then those two positions switch places, for
example [z, m, p, a] becomes [ m, p, a, z], but then how does 'a' get
to the top of the array? And is that formula of a[j], ... = ... a
simple equation you can use in many different ways or a more specific
method?

I tried to use only what I had learned in the tutorial up to the point
of the exercise, though I admit I flaked and looked up what the delete
method was. Here's what I wrote:

# declare variables and arrays

word = 'start'
unsortedList = []
sortedList = []
lowercase = []
trues = 0


# say hello

puts 'Hello. Type a word, press [ENTER] after every word, [ENTER] when
done: '


# get the input

while word != ''
   word = gets.chomp
   unsortedList.push word
end


# downcase the list so we can sort it

unsortedList.each do |i|
   lowercase.push i.downcase
end


# sort the list

while lowercase.length > 0

  lowercase.each do |i|

    lowercase.each do |j|

      if (i <= j)
      trues = trues + 1
      end

    end

    if (trues == lowercase.length)
    sortedList.push i
    lowercase.delete(i)
    trues = 0
    else
    trues = 0
    end

  end

end



# see the sorted list

puts '-' * 60
puts 'Your sorted list, dude:'
puts sortedList


# done


Needless to say this looks much more clunky to me though it was still a
lot of fun to do. If anyone can help with some of my questions or
comment on my solution that would be awesome, 


thanks, George